Thread-cutter for sewing machines



Feb. 9, 1937. P. SPAINE THREAD CUTTER FOR SEWING MACHINES Filed Oct. 4,1955 6 Sheets-Sheet l mime/x1 Feb. 9, 1937.

E. P. SPAINE THREAD CUTTER FOR SEWING MACH INES 6 sheets sheet 32 Filed001;. 4, 19 35 Feb. 9, .1937. E. P. SPAINE THREAD CUTTER FOR SEWINGMACHINES F led oat. 4. 1955 6 Sheets-Sheet 3 Edward 1. xs oaz'ne WibmaFeb. 9, 1937. E. P. SPAINE 2,070,029

THREAD CUTTER FOR SEWING MACHINES Eiled Oct. 4; 1935 e Sheets-Sheet 4Feb. 9, 1937. E. P. SPAINE I THREAD CUTTER FOR SEWING MACHINES FiledOct. 4, 1935 6 Sheets-Sheet 5 WMWveow y Feb. 9, 1937. E. P. SPAINETHREAD CUTTER FOR SEWING MACHINES Filed Oct. 4, 1935 6 Sheets-Sheet 6Edward 1? Sjmu'ne Patented Feb. 9, 1937 UNITED STATES PATENT OFFICETHREAD-CUTTER FOR SEWING MACHINES Application October 4, 1935, SerialNo. 43,467

9 Claims.

This invention relates to thread-cutting mechanisms for sewing machinesand more particularly to thread-cutting mechanisms for machines of thebuttonhole sewing type having stitch-forming mechanism and a work-clampwith means for relatively moving the stitch-forming mechanism andwork-clamp after the sewing of the buttonhole has been completed to drawout a length of thread from the needle-throat member at the under sideof the work; means being provided to separate the drawn out thread orthreads from the work and to out such thread or threads close to thelast stitch.

The invention aims to improve the thread-cutting mechanism disclosed inthe U. S. patent to E. B. Allen, No. 1,579,200, dated Apr. (3,1926, sothat it will handle work of any texture without damaging the work. Inthe mechanism of the Allen patent there is provided a scissors devicefor cutting the thread, which scissors device is moved along an upwardlyarched path transversely of the thread-lengths to be cut andsubstantially tangent to the under surface of the work, so that theblunt point or noseof the upper scissors blade will graze the undersurface of the work and enter between such surface and the threads to becut, deflecting the threads downwardly into the throat of the scissors.

The setting or adjustment of the operative radius of the scissors deviceof said patented construction is rather critical as, if too short theblunted point of the upper scissors blade is not likely to catch all ofthe threads and cord to be cut and, if too long, there is danger thatthe point, even though blunted, will snag the work, particularly if thelatter is of a loosely woven or knitted, sleazy or spongy nature.

According to the present improvement, the nose of the upper scissorsblade is made of special shape so that it cannot possibly snag the workbut will safely graze the latter and catch the threads to be cut,regardless of the character of the fabric in which the buttonhole isstitched. The principal characteristic of the nose of the present deviceis its broad, flat, duck-bill or spatula shape affording a thin and dullleading edge which is rounded horizontally along a broad-curve so thatit can safely graze the spongiest and sleaziest work without catchingthe fibres of the work.

With the above and other objects in view, as will hereinafter appear,the invention comprises the devices, combinations and arrangements ofparts hereinafter set forth and illustrated in the accompanying drawingsof a preferred embodiment of the invention, from which the severalfeatures of the invention and the advantages attained thereby will bereadily understood by those skilled in the art.

The invention will be better understood by reference to the followingdetailed description of certain specific embodiments of the inventionshown in the accompanying drawings, in which Fig. 1 is a side elevationof a buttonhole sewing machine embodying the invention. Fig. 2 is afragmentary front elevation of the machine. Fig. 3 is a plan view of themachine bed with the work-clamp removed. Fig. 4 is a plan View of thework-clamping elements and thread-cutting device, showing the nose ofthe latter entering between the threads to be cut and the under surfaceof the work. Fig. 5 is a section substantially on the line 5-5, Fig. 4.Fig. 6 is a fragmentary plan view of one of the lower auxiliaryworksupporting plates of the work-clamp. Fig. 7 is a sectionsubstantially on the line 7-4, Fig. 4. Fig. 8 is a bottom or under sideview of the thread-cutter of Figs. 1 to 7, inclusive. Fig. 9 is a sideview of the thread-cutter opposite to that shown in Fig. 2. Fig. 10 is adisassembled perspective view of the thread-cutter of Figs. 1 to 9,inclusive.

Figs. 11, 12, and 13 are, respectively, side elevation, bottom plan anddisassembled perspective views of a modified form of thread-cutter.Figs. 14, 15, and 16 are, respectively, side elevation, top plan anddisassembled perspective views of another modification of thethread-cutter, and Fig. 17 is a section on the line I'l-ll, Fig. 14.

The machine is constructed with a frame having a bed I from which risesthe standard 2 of the bracket-arm 3 terminating in the head 4.

The stitch-forming mechanism comprises the usual upper endwisereciprocatory and laterally vibratory needle 5 which cooperates with theunder stitch-forming instrumentalities carried by the rotary turret 6;such under instrumentalities including the usual threaded andnon-threaded loopers, l and 8, respectively, and the loopdetainers 9 andI0; being constructed substantially in accordance with the disclosure ofthe U. S. Patent to Allen et al., No. 1,372,473, dated Mar. 22, 1921.The turret 5 carries the usual needlethroat member ll having theneedle-receiving aperture l2 and the usual means for guiding the staycord l3 which is incorporated within the buttonhole overseam at theunder side of the work.

The stitch-forming mechanism is operated from the sewing shaft I 4 atthe rear end of which 5 5 is the usual belt-pulley l 5 and stop-motiondevice which is constructed substantially in accordance with thedisclosure of the Allen Patent No. 15,324; reissued Apr. 4, 1922, andincludes the tilting stop-motion lever [B which is fulcrumed at IT andcarries the stopping tooth i8 adapted for cooperation in a manner wellknown with the stopping cam I9 on the shaft 14.

Within the bed I is mounted the usual feedwheel 20 which makes onecomplete rotation per buttonhole-prcducing cycle and is driven duringthe sewing portion of such cycle by a suitable one- Way gear-drivenconnection (not shown) with the upright shaft 2! driven by the bevelgear connection 22, 23 with the sewing shaft I 4. The feedwheel isconnected to be driven at a higher speed both prior and subsequent tothe sewing period by the usual automatically operated clutch (not shown)intermediate the constantly running shaft 24 and the rapid-feed shaft25, which latter is permanently geared at 26 to the feed-wheel 20.

The work-clamp, which has the usual operative connections with thefeed-Wheel 20, comprises the lower work-supporting plates 27 and upperpivotally mounted clamping feet 28 sustained by the respectiveclamp-levers 20 fulcrumed at 3B. The work-clamp is closed automaticallyat the beginning of a buttonhole-producing cycle by a single oscillatorymovement of the usual clampclosing lever 3! which engages the arm 32 onthe clamp-closing rock-shaft 33, as explained in said Allen reissuedpatent. As soon as the workclamp is closed, the feed-wheel 20 andrapidfeed shaft 25 are coupled to the rapid-drive shaft 24, whereby thework-clamp is rapidly shifted forwardly from its initial position on thebed i to sewing position. When the work-clamp reaches sewing positionthe rapid-feed drive-shaft 24 is unclutched from the rapid-feed shaft 25and the stitch-forming mechanism is started, whereupon the feed-wheel 20and rapid-feed shaft 25 are more slowly driven through the usualgear-connections with the sewing shaft l4 and the work is moved in theusual path to space the stitches around the buttonhole. During thesewing around the eyelet end of the buttonhole the stitch-formingmechanism is slowly turned 180 about the vertical axis of the turret 5.When the sewing of the buttonhole is completed the stopmotion lever 15is tripped to stop the sewing shaft l4. The feed-wheel and rapid-feedshaft 25 are then again connected to the rapid-feed driveshaft 24 whichoperates to rapidly shift the workclamp rearwardly from sewing positionto the initial or buttonhole-cutting position on the bed I whichmovement of the work-clamp draws out from the needle-throat member Hfour thread lengths in close juxtaposition. One of these thread lengthsis the stay-cord 13. Another is the looper-thread 34. The remaining twoare the limbs of the last needle-thread loop 35 retained on theloop-detainer 9 when the machine comes to rest.

In the U. S. patent to Allen, No. 1,579,200 cited, and in U. S. patentsto Allen Nos. 1,600,206, of Sept. 21, 1926; 1,711,483, of May 7, 1929;1,852,-

634, of Apr. 5, 1932; 1,867,129, of July 12, 1932; and

in the U. S. Patent to Wood No. 1,938,128, of Dec. 5, 1933, there aredisclosed scissor devices for severing these drawn out thread-lengthsclose to the last stitch in the Work. The device of the presentinvention is broadly similar in principle and mode of operation to thatof the Allen Patent No. 1,579,200. It comprises the usualthreadcutter-carrying lever 36, Fig. 2, which is fulcrumed on the stud31 and is connected by the link 38 to the arm 39 of a lever fulcrumed at40 and having an arm 4|, Fig. 1, which has a rollerstud 42 entering thethread-cutter-actuating cam-slot 43 in the gear 26 on the rapid-feedshaft 25; the connections described being substantially the same asshown and described in said U. S. Patent No. 1,600,206, and thesubsequently issued patents above cited.

The lever 30 carries the thread-cutting device including a supportingshank 44, Figs. 8 and 9, carrying a fulcrum-stud 45 on which is mountedthe upper and lower blades 46, 47 of the scissors. The upper blade 45has a tail portion 48 which carries a screw 49 passing through a slot 50in the shank 45. By loosening the screw 49 the upper blade 56 may beadjusted about the fulcrumstud 45 to adjust the radius of action of thethread-catching point of the blade. The lower blade 41 has the usuallateral stud 5| which enters the groove 52 of the stationaryscissors-closing and opening cam 53.

In the device of the U. S. Patent No 1,579,200, the upper orledger-blade of the scissors is formed with a dulled and rounded leadingpoint so that it will not catch the fibres of the work while grazing thelatter. In accordance with the present improvement this pointed end hasbeen eliminated and the nose given a spatulate or duckbilled form bybeing considerably widened at one side of the vertical cutting plane ofthe scissors and formed with a broadly curved leading edge which maysafely graze the under surface of work of any texture without catchingthe fibres thereof.

As shown in Figs. 7 to 10, inclusive, this spatulate orduck-billed-shaped nose of the upper blade of the thread-cutter isconstituted by a separate element 54 having an attaching shank 55similar'to the shank 48 of the upper blade 46 of the scissors andattachable with the latter to the thread-cutter support 44 by thepivot-stud 45 and holding screw 49.

The point 56 of the upper blade of the scissors is in intimate contactwith the under surface of the spatulate member 54, so that the threadscaught by the advance of said member 54 readily slip under the point 56and into the throat of the scissors. The member 54 is only made separatefrom the blade 45 for convenience. Functionally it is integral with theblade 46. The spring 51 holds the lower scissors blade 41 in workingcontact with the upper, or ledger-blade 45. The broadly curved anddulled leading edge of the spatulate nose of the upper thread-cutterblade is preferably shaped as shown in Figs. 4 and 8. portion 58 iswidely spaced from the vertical cutting plane of the thread-cutter andis connected by an inclined portion 59 of gradually decreasing radius ofcurvature leading to the side edgeportion 55, Figs. 4 and 8, whichlatter is in line with the end of the buttonhole after the work has beenshifted from sewing position to initial position and the threads to beout have been drawn out from the needle-throat member I l, as usual, bysuch shifting of the work.

The lower clamp-plates 21, 2'! are provided with thread-cutter clearanceapertures a to permit the thread-cutter to move along its upwardlyarched path grazing the under surface of the work.

To dress up the machine, it is preferred to partially cover theseapertures a and to this end there are provided a pair of cover-plates 6|attached to the lower clamp-plates 21 by screws 62.

Its broadly curved foremost or leading The cover-plates 6| are thin andexpose the under surface portion of the work directly over theneedle-throat member H. The upper clamp-feet 28 may be provided withspring toe extensions 65 to press the work upon the cover-plates 6! inthe regions thereof at the sides of the needlethroat-member ii. Thebroadly curved tip end 58 of the nose 54 of the thread-cutter preferablypasses over the needle-throat-member I l and the threads issuingtherefrom, and under the portion 63 of the work in front of thebuttonhole 64. The inclined portion 59 of the nose 54 carries theseparation of the threads from the work up close to the last stitch 65where the threads are subsequently out by closure of the scissors in theusual manner. The fully advanced position of the thread-cutter nose 54is shown in dotted lines in Figs. 4 and 7. The threads are out, however,before the thread-cutter reaches. the end of its advancing movement; theclosure of the scissors being effected by the inclined upper end of thestationary cam-slot 52, Fig. 2, in the usual manner disclosed in U. S.Patent No. 1,579,200, previviously referred to.

It is to be understood that the use of the cover plates BI is notessential to the functioning of the present thread and work-separatingnose 54 of the thread-cutter, as the device functions just as well inthe absence of the cover-plates 6!; the duck-bill or spatulate nose 54scraping the threads I3, 34, and 35 from the under surface of the workwithout the slightest danger of catching the threads or fibres of thework.

The thread-gripper 61 seizes and removes the severed or waste loop 35 ofneedle-thread which is around the loop-detainer 9 when the machine comesto rest. This thread-gripper is preferably constructed and operatedsubstantially in accordance with the disclosure of said U. S. Patent No.1,579,200. After the threads are cut, the threadcutter is retracted toits normally out-of-the-way position, Fig. 2.

In Figs. 11, 12, and 13 there is illustrated a modified construction 68of the duck-bill shaped member. Its shape, in plan is substantially thesame as that of the first described member 54. It differs from the firstdescribed member 5a in that it does not overlie the point of the upperscissors blade 46', Fig. 13, but has a downturned fiange 69 against theside face ll of which the point II of the blade it bears. The flange 69guides the threads downwardly onto the point TI and into the throat ofthe scissors.

In Figs. 14 to 17, inclusive, there is illustrated a furthermodification of the present improvement. The thread-cutter supportingshank it has mounted thereon the duck-bill shaped member 12 havingsubstantially the same shape, in plan, as the previously describedmembers 54 and 68 but differing therefrom in being formed adjacent itsinner edge 13 with a slot M into which extends the sharpened uppercurved edge 15 of the knife 16 which is secured rigidly to the support44 by the screws T5, T8 affording the usual adjustment of the workingradius of the thread-cutter. The nose l2 acts to separate the threadsfrom the under surface of the work in the same manner as do the noses 54and 58 of the previously described modifications.

It will be understood that near the close of a buttonhole-producingcycle and after the workclamp has been rapidly shifted rearwardly to theposition shown in Fig. 4 to draw out the lengths of thread from theneedle-throat-member i i, the hump in the thread-cutter operating cam 43in the gear 26 on the rapid-feed shaft 25-effects a single up-and-downvibratory movement to the lever 39 which rocks the thread-cuttercarrying lever 36 about its fulcrum 31 and advances the thread-cutteralong its upwardly curved path in a direction transverse to thethread-lengths to be cut. The operating radius of the duck-bill shapednose of the thread-cutter is adjusted to graze fiatwise of itself theunder surface of the work and pass over the needle throat-member H andthe threads issuing therefrom. The inclined edge 59 and side edge 60 ofthe threadcutter nose effects a separation of the threads from the workat a point close to the last stitch where the threads are cut by thethread-cutter. It is of course understood that the pivotal axis 37 ofthe thread-cutter substantially intersects a vertical line normal to thework at the sewing point. In other words the thread-cutter axis 31 isdirectly under the sewing point, as viewed in Fig. 2, so that thethreads to be out are at the top of the curved path of travel of thethreadcutter.

Having thus set forth the nature of the invention, what I claim hereinis:

1. In a sewing machine in which that portion of the thread to be cutextends along and close to the surface of the work, means having aspatula shaped nose movable in a direction transverse to thethread-length and between the thread and the surface of the work toseparate the thread from the Work at a point close to the last stitch,and means to out said thread close to the last stitch.

2. A sewing machine having, in combination, stitch-forming mechanismincluding a reciprocatory needle and complemental loop-taking meansmounted at opposite sides of the plane of the work, athread-cutter-carrying lever pivoted at the loop-taker side of the workon an axis transverse to and in substantially intersecting relation witha line normal to the plane of the work at the sewing point, and athread-cutter carried by said lever and having a spatula shaped noseadapted when said lever is swung on its pivot to enter fiatwise ofitself between the under surface of the work and the thread leading fromthe last stitch to the sewing point, to separate the thread from thework close to the last stitch preparatory to the severing of the threadby the thread-cutter.

3. A buttonhole sewing machine having a frame comprising a bed andbracket-arm, stitch-forming mechanism including a needle and aneedlethroat member, a work-clamp, means for relatively moving thestitch-forming mechanism and work-clamp to sew around a buttonhole andto relatively separate the buttonhole and stitchforming mechanismlengthwise of the machine bed subsequent to the sewing operation,thereby drawing out a length of thread from the needlethroat member, anda thread-cutter pivoted on an axis extending lengthwise of the machinebed, said thread-cutter having a thin spatula shaped nose adapted toscrape the thread from the under surface of the work and separate thethread from the work close to the last stitch preparatory to thethread-cutting action.

4. In a sewing machine adapted to perform a predetermined sewingoperation and then come to rest, the combination with stitch-formingmechanism and work-holding means movable relative to each other duringand subsequent to a relative movement after the sewing operation drawingout a length of thread from the needlethroat member, means movable overthe needlethroat member in a direction transverse to the length ofthread to a position between the length of thread and the work, saidmeans having a broadly curved leading edge, and means to sever thethread close to the last stitch. V

5. In a sewing machine adapted to perform a predetermined sewingoperation and then come to rest, the combination with stitch-formingmechanism and work-holding means movable relative to each other duringand subsequent to the sewing operation, of a needle-throat memberthrough which the thread is led to the work, the relative movement afterthe sewing operation drawing out a length of thread from theneedlethroat member, of means movable transversely of the length of thethread and having a thin and wide nose with a broadly curved andnon-pointed leading edge to separate the thread from the work close tothe last stitch, and means to sever the thread.

6. In a sewing machine adapted to perform a predetermine sewingoperation and then come to rest, the combination with stitch-formingmechanism and work-holding means movable relative to each other duringand subsequent to the sewing operation, of a needle-throat memberthrough which the thread is led to the work, the relative movement afterthe sewing operation drawing out a length of thread from the needle--throat member, of means movable in a curved path transversely of thelength of thread and having a thin wide nose with a broad tip and aninclined edge leading from said tip to separate the thread from the workclose to the last stitch, and means to sever the thread.

7. In a sewing machine adapted to perform a predetermined sewingoperation and then come to rest, the combination with stitch-formingmechanism and work-holding means movable relative to each other duringand subsequent to the sewing operation, of a needle-throat memberthrough which the thread is led to the work, the relative movement afterthe sewing operation drawing out a length of thread from theneedlethroat member, means movable transversely of the length of threadand having a thin wide nose with a broadly curved tip and an inclinededge portion leading from said tip to pass between the thread and thework, and means to sever the thread;

8. A sewing machine thread-cutter having a thread-cutting blade and athin wide nose substantially normal to the cutting plane of said blade;the extreme end of said nose being broadl curved in the plane thereof.

9. In a sewing machine adapted to perform a predetermined sewingoperation and then come to rest, the combination with stitch-formingmechanism and work-holding means movable relative to each other duringand subsequent to the sewing operation, of a needle-throat memberthrough which the thread is led to the work, the relative movement afterthe sewing operation drawing out a length of thread from theneedlethroat member, of thread and work-separating means having a thin,broadly curved and nonpointed leading edge movable transversely of thethread and between the latter and the work, and means to sever thethread.

EDWARD P. SPAINE.

